1. Field of the Invention
This invention relates generally to high performance semiconductor devices with a barrier layer formed of a layer of amorphous silicon or polysilicon implanted with nitrogen. More specifically, this invention relates to high performance semiconductor devices with a barrier layer formed of a layer or amorphous silicon or polysilicon implanted with nitrogen and having a hydrogen getter layer formed under the barrier layer.
2. Discussion of the Related Art
The semiconductor industry is characterized by the dual requirements of an increase in the speed of integrated circuits and an increase in the density of elements in those integrated circuits. These two requirements have thus become the two major goals of the design engineers in their design and manufacturing efforts concerned with MOSFETs and other semiconductor devices, such as volatile and nonvolatile memory devices. Increasing the density of elements in integrated circuits means that smaller channel lengths and widths have to be used. As the dimensions of semiconductor devices decreased, the existing "long-channel" performance models for MOSFET devices predicted that the decrease in the channel length, L, or the gate oxide thickness, T.sub.ox, would increase I.sub.DSAT. However, as MOSFET devices were scaled below approximately 2 .mu.m, effects not predicted by the existing long channel models were observed and the unexpected effects were thereafter termed "short-channel" effects.
As device dimensions of MOSFETs continued to decrease, it was determined that problems associated with the short-channel effects could be placed in two general categories: (1) the problem of increased leakage current when the MOSFET is off and (2) reliability problems associated with short-channel and thin gate oxide device structures.
Some of the reliability problems that arise in short-channel and thin gate oxide MOSFETs include; (1) thin gate oxide breakdown, (2) device degradation due to hot-carrier effects, (3) reliability problems associated with interconnects between MOSFETs and (4) reliability problems associated with local interconnects. One of the major problems associated with semiconductor devices other than MOSFETs involves high-temperature data retention in nonvolatile memory cells. The two problems that are of particular interest are device degradation due to hot-carrier effects and high-temperature data retention problems in nonvolatile memory cells.
It has been observed that there are high-temperature data retention problems in nonvolatile memory cell arrays such as EPROMs, FLASH EPROMs, and E.sup.2 PROMs. It has been postulated that the poor high-temperature data retention is due to mobile hydrogen atoms that diffuse to the floating gate in a nonvolatile memory cell and cause the charge on the floating gate to be lost.
The reduced memory cell size and high-performance logic circuits has necessitated the use of borderless contacts and local interconnects. The borderless contacts and local interconnects have required the use of a barrier layer such as an etch stop layer or diffusion protect layer. The prior art developed a low-temperature, damascene-tungsten local interconnect for a 0.25 .mu.m channel CMOS technology with trench isolation. One such prior art structure is described in "A Low-Temperature Local Interconnect Process in a 0.25-.mu.m-channel CMOS Logic Technology with Shallow Trench Isolation," by J. Givens, S. Geissler, O. Cain, W. Clark, C Koburger, J. Lee, 1994 VMIC Conference. However, the prior art includes the use of silicon nitride films that have high hydrogen content. The high hydrogen content has caused problems as described in the article "Effects of Silicon Nitride Encapsulation on MOS Device Stability," by R. C. Sun, J. T. Clemens and J. T. Nelson, IEEE 1980. This article describes a new threshold instability phenomenon observed in MOS transistors encapsulated with plasma deposited silicon nitride films and describes a series of experiments which indicated that the instability was due to a chemical effect associated with hydrogen in the silicon nitride films. The article postulated that the formation of surface states and fixed charges in the channel region was due to the interaction of hot carriers with hydrogen present at the interface and was the basic mechanism causing the instability.
Therefore, what is needed are semiconductor devices that have low amounts of free hydrogen and methods of manufacturing such low hydrogen content semiconductor devices.